Multi-station dangerous condition alarm system incorporating alarm and chirp origination feature

• US 6,121,874 A
• Filed: 05/25/1999
• Issued: 09/19/2000
• Est. Priority Date: 07/29/1997
• Status: Expired due to Term

• Current Assignee: Maple Chase Company
• Original Assignee: Maple Chase Company
• Inventors: O'Donnell, Thomas J.
• Primary Examiner(s): POPE, DARYL C
• Application Number:
  US09/318,698
• Time in Patent Office: 483 Days
• Field of Search: 340/506, 340/512, 340/517, 340/825.2, 340/825.14, 340/825.57, 340/825.61
• US Class Current: 340/506
• CPC Class Codes: G08B 17/00 Fire alarms; Alarms responsive to explosion
• CPC Class Codes: G08B 25/009 Signalling of the alarm condition to a substation whose identity is signalled to a central station, e.g. relaying alarm signals in order to extend communication range
• CPC Class Codes: G08B 27/00 Alarm systems in which the alarm condition is signalled from a central station to a plurality of substations
• CPC Class Codes: G08B 29/181 due to failing power supply
• CPC Class Codes: G08B 7/06 using electric transmission , e.g. involving audible and visible signalling through the use of sound and light sources

Abstract

In a dangerous condition sensing alarm system which includes a plurality of interconnected dangerous condition sensing units, such as smoke detectors, of the general type in which each unit responds to an apparently sensed dangerous condition by issuing an audible alarm and also by transmitting, from an input/output terminal, a signal to the other units (received as an external alarm signal at corresponding input/output terminals of the other units) so that an alarm condition sensed by any one of the units results in alarms being sounded by all the units, a unit initiating an alarm (which may be false) is marked by an alarm origination circuit. The alarm origination circuit includes a visual indicator (such as an LED) and a latch device (such as an SCR) connected in-circuit such that, when the SCR is turned "on", the LED is activated and remains lit until the SCR is turned "off". The SCR is turned "on" by a signal developed from the audio frequency drive to the unit annunciator unless this action has been earlier inhibited by an electronic switch which, just before the local alarm is sounded, places a virtual ground on the SCR gate. The electronic switch is activated by an external alarm signal more quickly than the local unit'"'"'s audio frequency drive is established. Thus, an external alarm signal will not cause the LED to light.

Claims

1. In a dangerous condition sensing alarm system including a plurality of interconnected dangerous condition sensing units in which each unit includes means for sensing a dangerous condition and issuing an audible alarm from an annunciator in response thereto and for transmitting, from an input/output terminal, a signal to the other units, received at corresponding input/output terminals of such other units, in order than an alarm sensed by any one of the units results in alarms being issued by all the units, the improvement in which an alarm origination circuit is incorporated into each of the units to provide an indication as to which unit apparently sensed a dangerous condition which caused all the units to sound an alarm, each alarm origination circuit in a local unit comprising:

A) an alarm origination indicator;

B) a latch connected in-circuit with said alarm origination indicator such that, when said latch is turned "on", said alarm origination indicator is activated and remains activated until said latch is turned "off";

C) latch actuation means responsive to the issuance of an alarm by the local unit by developing a local alarm signal which will cause said latch to be turned "on" unless such action has been inhibited, said local alarm signal being developed from an audio drive signal applied to the annunciator;

D) signal level delay means connected between the input/output terminal and an electrical point common to all the interconnected units, said signal level delay means being adapted to delay an external alarm signal received from an input/output terminal of another unit from instituting the issuance of an alarm by the local unit; and

E) latch inhibit means coupled to said signal level delay means and adapted to sense the presence of an external alarm signal before an alarm is issued by the local unit in response to the external alarm signal, said latch inhibit means being responsive to sensing an external alarm signal by inhibiting said latch from being turned "on" due to the subsequent issuance of an alarm by the local unit.

2. The alarm origination circuit of claim 1 in which said latch comprises a silicon controlled rectifier having a gate and in which said local alarm signal is coupled to said gate.

3. The alarm origination circuit of claim 2 in which said signal level delay means comprises a resistor connected between the input/output terminal and the electrical point common to all the interconnected units and a capacitor connected between the input/output terminal and a reference potential such that an external alarm signal charges said capacitor through said resistor and said latch inhibit means is activated before an alarm is issued by the local unit.

4. The alarm origination circuit of claim 3 in which said latch inhibit means includes an electronic switch responsive to an external alarm signal to apply a virtual ground to said gate to thereby inhibit said silicon controlled rectifier from being turned "on".

5. The alarm origination circuit of claim 1 in which said alarm origination indicator is a light emitting diode connected intermediate a voltage source and said silicon controlled rectifier such that, when said silicon controlled rectifier is latch "on", current flows through said light emitting diode which is therefore illuminated to indicate that the local unit apparently sensed a dangerous condition and initiated a system alarm.

6. The alarm origination circuit of claim 2 in which said alarm origination indicator is a light emitting diode connected intermediate a voltage source and said silicon controlled rectifier such that, when said silicon controlled rectifier is latched "on", current flows through said light emitting diode which is therefore illuminated to indicate that the local unit apparently sensed a dangerous condition and initiated a system alarm.

7. The alarm origination circuit of claim 3 in which said alarm origination indicator is a light emitting diode connected intermediate a voltage source and said silicon controlled rectifier such that, when said silicon controlled rectifier is latched "on", current flows through said light emitting diode which is therefore illuminated to indicate that the local unit apparently sensed a dangerous condition and initiated a system alarm.

8. The alarm origination circuit of claim 4 in which said alarm origination indicator is a light emitting diode connected intermediate a voltage source and said silicon controlled rectifier such that, when said silicon controlled rectifier is latched "on", current flows through said light emitting diode which is therefore illuminated to indicate that the local unit apparently sensed a dangerous condition and initiated a system alarm.

9. The alarm origination circuit of claim 2 which further includes low battery identification means for indicating if a battery in the local unit is sufficiently drained as to be unreliable for energizing the unit, said low battery identification means including test means for periodically momentarily loading the battery and driving said annunciator to issue a characteristic audible signal each time said battery tests below a predetermined acceptable level of drain such that said characteristic audible signal alternatively develops said local alarm signal and turns said latch "on", thereby indicating that the local unit is the source of the characteristic audible signal and accordingly has a battery which should be replaced.

10. The alarm origination circuit of claim 3 which further includes low battery identification means for indicating if a battery in the local unit is sufficiently drained as to be unreliable for energizing the unit, said low battery identification means including test means for periodically momentarily loading the battery and driving said annunciator to issue a characteristic audible signal each time said battery tests below a predetermined acceptable level of drain such that said characteristic audible signal alternatively develops said local alarm signal and turns said latch "on", thereby indicating that the local unit is the source of the characteristic audible signal and accordingly has a battery which should be replaced.

11. The alarm origination circuit of claim 4 which further includes low battery identification means for indicating if a battery in the local unit is sufficiently drained as to be unreliable for energizing the unit, said low battery identification means including test means for periodically momentarily loading the battery and driving said annunciator to issue a characteristic audible signal each time said battery tests below a predetermined acceptable level of drain such that said characteristic audible signal alternatively develops said local alarm signal and turns said latch "on", thereby indicating that the local unit is the source of the characteristic audible signal and accordingly has a battery which should be replaced.

12. The alarm origination circuit of claim 5 which further includes low battery identification means for indicating if a battery in the local unit is sufficiently drained as to be unreliable for energizing the unit, said low battery identification means including test means for periodically momentarily loading the battery and driving said annunciator to issue a characteristic audible signal each time said battery tests below a predetermined acceptable level of drain such that said characteristic audible signal alternatively develops said local alarm signal and turns said latch "on", thereby indicating that the local unit is the source of the characteristic audible signal and accordingly has a battery which should be replaced.

13. The alarm origination Circuit of claim 7 which further includes low battery identification means for indicating if a battery in the local unit is sufficiently drained as to be unreliable for energizing the unit, said low battery identification means including test means for periodically momentarily loading the battery and driving said annunciator to issue a characteristic audible signal each time said battery tests below a predetermined acceptable level of drain such that said characteristic audible signal alternatively develops said local alarm signal and turns said latch "on", thereby indicating that the local unit is the source of the characteristic audible signal and accordingly has a battery which should be replaced.

14. The alarm origination circuit of claim 8 which further includes low battery identification means for indicating if a battery in the local unit is sufficiently drained as to be unreliable for energizing the unit, said low battery identification means including test means for periodically momentarily loading the battery and driving said annunciator to issue a characteristic audible signal each time said battery tests below a predetermined acceptable level of drain such that said characteristic audible signal alternatively develops said local alarm signal and turns said latch "on", thereby indicating that the local unit is the source of the characteristic audible signal and accordingly has a battery which should be replaced.

15. The alarm origination circuit of claim 1 in which said signal level delay means comprises a resistor connected between the input/output terminal and the electrical point common to all the interconnected units and a capacitor connected between the input/output terminal and a reference potential such that an external alarm signal charges said capacitor through said resistor and said latch inhibit means is activated before and alarm is issued by the local unit.

16. In a dangerous condition sensing alarm system including a plurality of interconnected dangerous condition sensing units in which each unit includes means for sensing a dangerous condition and issuing in response thereto and for transmitting, from an input/output terminal, a signal to the other units, received at corresponding input/output terminals of such other units, in order than an alarm sensed by any one of the units results in alarms being issued by all the units, the improvement in which an alarm origination circuit is incorporated into each of the units to provide an indication as to which unit apparently sensed a dangerous condition which caused all the units to sound an alarm, each alarm origination circuit in a local unit comprising:

B) an alarm origination indicator;

B) a latch connected in-circuit with said alarm origination indicator such that, when said latch is turned "on", said alarm origination indicator is activated and remains activated until said latch is turned "off";

C) latch actuation means responsive to the issuance of an alarm by the local unit by developing a local alarm signal which will cause said latch to be turned "on" unless such action has been inhibited;

D) signal level delay means connected between the input/output terminal and an electrical point common to all the interconnected units, said signal level delay means being adapted to delay an external alarm signal received from an input/output terminal of another unit from instituting the issuance of an alarm by the local unit, said signal level delay means comprising a resistor connected between the input/output terminal and the electrical point common to all the interconnected units and a capacitor connected between the input/output terminal and a reference potential such that an external alarm signal charges said capacitor through said resistor and said latch inhibit means is activated before an alarm is issued by the local unit; and

E) latch inhibit means coupled to said signal level delay means and adapted to sense the presence of an external alarm signal before an alarm is issued by the local unit in response to the external alarm signal, said latch inhibit means being responsive to sensing an external alarm signal by inhibiting said latch from being turned "on" due to the subsequent issuance of an alarm by the local unit.

17. The alarm origination circuit of claim 16 in which said latch comprises a silicon controlled rectifier having a gate and in which said local alarm signal is coupled to said gate.

18. The alarm origination circuit of claim 17 in which said signal level delay means comprises a resistor connected between the input/output terminal and the electrical point common to all the interconnected units and a capacitor connected between the input/output terminal and a reference potential such that an external alarm signal charges said capacitor through said resistor and said latch inhibit means is activated before an alarm is issued by the local unit.

19. The alarm origination circuit of claim 18 in which said latch inhibit means includes an electronic switch responsive to an external alarm signal to apply a virtual ground to said gate to thereby inhibit said silicon controlled rectifier from being turned "on".

20. The alarm origination circuit of claim 16 in which said alarm origination indicator is a light emitting diode connected intermediate a voltage source and said silicon controlled rectifier such that, when said silicon controlled rectifier is latch "on", current flows through said light emitting diode which is therefore illuminated to indicate that the local unit apparently sensed a dangerous condition and initiated a system alarm.

21. The alarm origination circuit of claim 17 in which said alarm origination indicator is a light emitting diode connected intermediate a voltage source and said silicon controlled rectifier such that, when said silicon controlled rectifier is latched "on", current flows through said light emitting diode which is therefore illuminated to indicate that the local unit apparently sensed a dangerous condition and initiated a system alarm.

22. The alarm origination circuit of claim 18 in which said alarm origination indicator is a light emitting diode connected intermediate a voltage source and said silicon controlled rectifier such that, when said silicon controlled rectifier is latched "on", current flows through said light emitting diode which is therefore illuminated to indicate that the local unit apparently sensed a dangerous condition and initiated a system alarm.

23. The alarm origination circuit of claim 19 in which said alarm origination indicator is a light emitting diode connected intermediate a voltage source and said silicon controlled rectifier such that, when said silicon controlled rectifier is latched "on", current flows through said light emitting diode which is therefore illuminated to indicate that the local unit apparently sensed a dangerous condition and initiated a system alarm.

24. The alarm origination circuit of claim 17 which further includes low battery identification means for indicating if a battery in the local unit is sufficiently drained as to be unreliable for energizing the unit, said low battery identification means including test means for periodically momentarily loading the battery and driving said annunciator to issue a characteristic audible signal each time said battery tests below a predetermined acceptable level of drain such that said characteristic audible signal alternatively develops said local alarm signal and turns said latch "on", thereby indicating that the local unit is the source of the characteristic audible signal and accordingly has a battery which should be replaced.

25. The alarm origination circuit of claim 18 which further includes low battery identification means for indicating if a battery in the local unit is sufficiently drained as to be unreliable for energizing the unit, said low battery identification means including test means for periodically momentarily loading the battery and driving said annunciator to issue a characteristic audible signal each time said battery tests below a predetermined acceptable level of drain such that said characteristic audible signal alternatively develops said local alarm signal and turns said latch "on", thereby indicating that the local unit is the source of the characteristic audible signal and accordingly has a battery which should be replaced.

26. The alarm origination circuit of claim 19 which further includes low battery identification means for indicating if a battery in the local unit is sufficiently drained as to be unreliable for energizing the unit, said low battery identification means including test means for periodically momentarily loading the battery and driving said annunciator to issue a characteristic audible signal each time said battery tests below a predetermined acceptable level of drain such that said characteristic audible signal alternatively develops said local alarm signal and turns said latch "on", thereby indicating that the local unit is the source of the characteristic audible signal and accordingly has a battery which should be replaced.

27. The alarm origination circuit of claim 20 which further includes low battery identification means for indicating if a battery in the local unit is sufficiently drained as to be unreliable for energizing the unit, said low battery identification means including test means for periodically momentarily loading the battery and driving said annunciator to issue a characteristic audible signal each time said battery tests below a predetermined acceptable level of drain such that said characteristic audible signal alternatively develops said local alarm signal and turns said latch "on", thereby indicating that the local unit is the source of the characteristic audible signal and accordingly has a battery which should be replaced.

28. The alarm origination Circuit of claim 22 which further includes low battery identification means for indicating if a battery in the local unit is sufficiently drained as to be unreliable for energizing the unit, said low battery identification means including test means for periodically momentarily loading the battery and driving said annunciator to issue a characteristic audible signal each time said battery tests below a predetermined acceptable level of drain such that said characteristic audible signal alternatively develops said local alarm signal and turns said latch "on", thereby indicating that the local unit is the source of the characteristic audible signal and accordingly has a battery which should be replaced.

29. The alarm origination circuit of claim 23 which further includes low battery identification means for indicating if a battery in the local unit is sufficiently drained as to be unreliable for energizing the unit, said low battery identification means including test means for periodically momentarily loading the battery and driving said annunciator to issue a characteristic audible signal each time said battery tests below a predetermined acceptable level of drain such that said characteristic audible signal alternatively develops said local alarm signal and turns said latch "on", thereby indicating that the local unit is the source of the characteristic audible signal and accordingly has a battery which should be replaced.

30. The alarm origination circuit of claim 16 in which the alarm issued by the local unit is an audible alarm issued by an annunciator and in which said local alarm signal is developed from an audio drive signal applied to said annunciator.

31. A sensing alarm device, for providing an alarm indication of a detected dangerous condition within an installed space and, alternately, for providing an alarm indication for a dangerous condition detected by an external sensing alarm device in communication therewith, comprising:

a condition sensor, for sensing a dangerous condition within the installed space and for providing a sensor output signal in response thereto;

a detector circuit, for providing a self detected alarm condition signal in response to the presence of a sensor output signal;

input/output (I/O) circuitry, for presenting said self detected alarm condition signal to, and for receiving an externally detected alarm condition signal from, an external sensing alarm device in communication therewith;

an annunciator, for issuing the alarm indication in response to the presence alone of said self detected alarm condition signal and, alternately, in the presence alone of said externally detected alarm condition signal and, alternately, in the presence of said self detected alarm condition signal jointly with said externally detected alarm condition signal; and

an alarm origination indicator circuit, including an indicator device, and responsive to said detector circuit, for actuating said indicator device in the presence of said self detected alarm condition signal to identify the sensing alarm device as the originating alarm source.

32. The device of claim 31 further comprising:

a test switch cooperating with the condition sensor for selectively actuating the condition sensor such that the sensor output signal is generated; and

a circuit, cooperating with the test switch, for inhibiting actuation of the alarm origination indicator circuit.

33. The device of claim 31 further comprising:

a battery;

a battery monitoring circuit for generating a signal indicative of a failing battery condition; and

wherein

the detector circuit, in response to the signal indicative of a failing battery condition, further provides a battery alarm signal to the annunciator and to the alarm origination circuit, causing the annunciator to issue a distinctive alarm associated with a low battery condition, and causing the alarm origination circuit to actuate the indicator device.

34. The device of claim 33 further comprising:

a test switch cooperating with the condition sensor for selectively actuating the condition sensor such that the sensor output signal is generated; and

a circuit, cooperating with the test switch, for inhibiting actuation of the alarm origination indicator circuit.

35. The device of claim 31 wherein the alarm origination indicator circuit further comprises a latching device operable, alternately, in a latched on state to actuate said indicator device and in an unlatched state to de-actuate said indicator device said latching device being latched on by said alarm origination indicator circuit in response to the presence of a self detected alarm condition signal and, alternately, to the presence of said battery alarm signal.

37. The apparatus of claim 31 wherein the condition sensor comprises an ion chamber detector, and said indicia of a dangerous condition comprises smoke.

38. The device of claim 35 wherein:

the indicator device comprises an LED of predetermined color; and

the latching device comprises a Silicon Controlled Rectifier with anode and cathode disposed to selectively provide a current path through the LED, and a gate responsive to said self detected alarm condition signal and, alternately, to said battery alarm signal.

36. A dangerous condition sensing alarm device, adapted to be used in a system comprising an interconnected plurality of such dangerous condition sensing devices, and to receive I/O signals from other devices in the system indicative of the other device having sensed an apparent dangerous condition, the device comprising:

a condition sensor for sensing indicia of the dangerous condition, and in response thereto, generating a sensor output signal;

a detector circuit, receptive of the sensor output signal, and, when connected in the system, I/O signals from other devices, for selectively generating;

in response to an I/O signal from another device in the system, subsequent to receiving the I/O signal, a first detector circuit output signal; and

in response to the sensor output signal, the first detector circuit output signal and a second detector circuit output signal, the second detector circuit output signal being transmitted as the I/O signal to the detector circuits of the other devices in the system such that a dangerous condition sensed by any one of the devices in the system results in alarms being issued by all of the devices;

an annunciator, responsive to the first detector circuit output signal, for issuing an alarm; and

,

an indicator circuit, including an indicator device and having the first detector circuit output signal and I/O signals from other devices applied thereto, for, once actuated, generating a predetermined indication of an alarm having been originated by that particular device, the indicator circuit being actuated in response to application of the first detector circuit output signal prior to application of an I/O signal from another device.